diff --git a/tools/build_api.py b/tools/build_api.py
index 7a267a0405..790b1bcb65 100644
--- a/tools/build_api.py
+++ b/tools/build_api.py
@@ -438,6 +438,18 @@ def scan_resources(src_paths, toolchain, dependencies_paths=None,
     # Set the toolchain's configuration data
     toolchain.set_config_data(toolchain.config.get_config_data())
 
+    if  (hasattr(toolchain.target, "release_versions") and
+            "5" not in toolchain.target.release_versions and
+            "rtos" in toolchain.config.lib_config_data):
+        if "Cortex-A" in toolchain.target.core:
+            raise NotSupportedException(
+                ("%s Will be supported in mbed OS 5.6. "
+                    "To use the %s, please checkout the mbed OS 5.4 release branch. "
+                    "See https://developer.mbed.org/platforms/Renesas-GR-PEACH/#important-notice "
+                    "for more information") % (toolchain.target.name, toolchain.target.name))
+        else:
+            raise NotSupportedException("Target does not support mbed OS 5")
+
     return resources
 
 def build_project(src_paths, build_path, target, toolchain_name,
@@ -519,17 +531,6 @@ def build_project(src_paths, build_path, target, toolchain_name,
     try:
         # Call unified scan_resources
         resources = scan_resources(src_paths, toolchain, inc_dirs=inc_dirs)
-        if  (hasattr(toolchain.target, "release_versions") and
-             "5" not in toolchain.target.release_versions and
-             "rtos" in toolchain.config.lib_config_data):
-            if "Cortex-A" in toolchain.target.core:
-                raise NotSupportedException(
-                    ("%s Will be supported in mbed OS 5.6. "
-                     "To use the %s, please checkout the mbed OS 5.4 release branch. "
-                     "See https://developer.mbed.org/platforms/Renesas-GR-PEACH/#important-notice "
-                     "for more information") % (toolchain.target.name, toolchain.target.name))
-            else:
-                raise NotSupportedException("Target does not support mbed OS 5")
 
         # Change linker script if specified
         if linker_script is not None:
diff --git a/tools/project.py b/tools/project.py
index 05f5c0a7d0..ff59f5b9d4 100644
--- a/tools/project.py
+++ b/tools/project.py
@@ -20,6 +20,7 @@ from tools.utils import argparse_filestring_type, argparse_profile_filestring_ty
 from tools.utils import argparse_force_lowercase_type
 from tools.utils import argparse_force_uppercase_type
 from tools.utils import print_large_string
+from tools.utils import NotSupportedException
 from tools.options import extract_profile, list_profiles, extract_mcus
 
 def setup_project(ide, target, program=None, source_dir=None, build=None, export_path=None):
@@ -246,11 +247,13 @@ def main():
     profile = extract_profile(parser, options, toolchain_name, fallback="debug")
     if options.clean:
         rmtree(BUILD_DIR)
-    export(mcu, options.ide, build=options.build,
-           src=options.source_dir, macros=options.macros,
-           project_id=options.program, zip_proj=zip_proj,
-           build_profile=profile, app_config=options.app_config)
-
+    try:
+        export(mcu, options.ide, build=options.build,
+               src=options.source_dir, macros=options.macros,
+               project_id=options.program, zip_proj=zip_proj,
+               build_profile=profile, app_config=options.app_config)
+    except NotSupportedException as exc:
+        print "[ERROR] %s" % str(exc)
 
 if __name__ == "__main__":
     main()